The present invention relates to a lubricating system for an internal combustion engine. More particularly, the present invention relates to a four-cycle engine for use in powering a water propulsion device of a watercraft, and a lubricating system for the engine.
Two-cycle engines are used to power watercraft, including smaller watercraft known as xe2x80x9cpersonalxe2x80x9d watercraft. These engines have the advantage that they are fairly powerful, and relatively lightweight and compact.
One particular disadvantage to the two-cycle engine is its emission content. Two-cycle engines exhaust large quantities of carbon monoxide (CO) and various hydrocarbons. When measures are taken to reduce the emission content of the two-cycle engine, other generally undesirable consequences result, such as an increase in the weight of the engine, a reduction of its power output or the like.
Four-cycle engines are commonly used as a power plant in other applications, such as automobiles. These engines have the advantage that their emission content is desirably lower and the engines have a high power output.
On the other hand, four-cycle engines are generally arranged with oil-filled crankcases or reservoirs positioned at the bottom of the cylinder block. This impedes use of the four-cycle engine in this type of watercraft. In particular, when this type of engine is mounted in a watercraft in a manner in which the drive shaft is generally horizontally extending, the drive shaft must be elevated well above the hull of the watercraft in order to accommodate the oil reservoir extending below the engine.
At the same time, it is desirable for the impeller shaft which drives the water propulsion device for the watercraft to be positioned along the hull of the watercraft. If the propulsion device is raised upwardly, or if the impeller shaft is angled, the efficiency of the water propulsion device decreases dramatically. This causes a decrease in water propulsion force. Thus, when the standard four-cycle engine is mounted in a watercraft, the drive shaft is oriented in a manner incompatible with the impeller shaft of the propulsion unit.
It is desired to provide a watercraft with a four-cycle engine for powering a generally horizontally extending impeller shaft where the engine is supplied with adequate lubrication, and yet the propulsion efficiency of the watercraft""s propulsion unit, remains high.
In accordance with the present invention, an arrangement is provided whereby a watercraft may be powered by a four-cycle internal combustion engine and still retain high propulsion efficiency. In each arrangement, a crankshaft of the engine is in driving relation with an impeller shaft which drives a water propulsion device of the watercraft. Preferably, the water propulsion device comprises a water propulsion passage having an inlet and outlet and extending through a hull of the watercraft, with an impeller positioned in the passage for expelling water out the outlet.
In accordance with the present invention, the four-cycle engine is arranged so that the crankshaft thereof is interrelated with the lubricating oil reservoir so that the crankshaft does not contact the lubricant in the oil reservoir during the running of the engine.
In the presently preferred arrangement, the four-cycle engine is provided with a dry-sump type lubricating system. In this arrangement the oil reservoir is provided at a location other than the bottom of the engine, whereby the engine may be oriented so that the crankshaft extends along an axis near the bottom of the hull. The crankshaft extends along the same axis which the impeller shaft extends, with the impeller shaft and crankshaft in driving relation.
Further objects, features, and advantages of the present invention over the prior art will become apparent from the detailed description of the drawings which follows, when considered with the attached; figures.